In the design of thermally resistive doors, it has long been known to provide a generally boxlike metallic shell and to fill same with some form of insulative material such as a plastics foam, usually foamed in place. These have been highly satisfactory due to the structural strength provided by the metal shell which is usually of rolled steel sheet, and the insulative quality of the plastics foam. However, since such constructions have normally involved a fully boxlike design, this has meant that there was a metallic connection between the inner and outer panels thereof and hence a highly heat conductive path therebetween. While this has not destroyed the value of an insulative door as described, it has nevertheless diminished its full insulative potential. Hence, it has long been desired to provide a door having both the structural strength and the surface resistance to impact obtained from the steel boxlike construction together with the heat insulative qualities of the foam filling, yet in some manner to interrupt the previously existing heat conductive path between the inner and outer panels thereof. Previous attempts to do this have often merely substituted other heat conductive paths, resulted in a weaker door or made it impossible to use a foam which is injected under pressure into the interior of the door.
Accordingly, the objects of the invention include:
1. To provide a heat insulative door having a maximum level of heat insulative qualities without sacrifice in structural strength or surface impact resistance.
2. To provide a door, as aforesaid, which can be fully sealed in order to render possible the use of a pressure injected foam into the cavity therewithin.
3. To provide a door, as aforesaid, whose metallic parts can be made of easily rolled sheet metal components which are of simple design and which can be readily assembled by simple techniques.
4. To provide a door construction, as aforesaid, utilizing seals of plastics material which are of simple design and readily extrudable to hold the cost thereof to a minimum.
5. To provide a door, as aforesaid, whose basic design can be expressed in a variety of different specific designs as desired to meet a variety of particular building closure requirements, all of which will require only components of relatively simple design which can be inexpensively assembled but which will provide a high degree of satisfaction in use.
Other objects and purposes of the invention will be apparent to persons acquainted with products of this general type upon reading the following specification and inspection of the accompanying drawings.